Large supplies of fuel and other liquids are maintained in large storage tanks in various strategic locations where the fuel can be pumped into trucks and other vehicles for transportation to the consumer. The typical fuel storage tank is fabricated from metal, such as steel, and a sump is located at the bottom of the tank.
One of the problems typically encountered in fuel storage tanks is the accumulation of water inside the tank. Vapor condenses on the walls of the tank and the water drains down the walls of the tank to the surface of the fuel, and since the water is heavier than the fuel, the water settles in the bottom of the tank. As a quality control measure, the water that condenses and settles to the tank bottom must be removed before the fuel is pumped from the tank, so that the fuel being delivered to a customer is free of water. As a maintenance measure, the water must be kept out of the pipeline equipment so as to prevent rust and corrosion and mechanical failure of the equipment. Thus, the tank must be drained periodically of the water which settles in the bottom of the tank.
It is common practice to drain the water from the bottom of large fuel tanks by the use of a permanently installed drain conduit which has one of its ends in the sump of the tank and the other of its ends extending out of the tank. A valve outside the tank is manipulated to open and close the drain conduit, and an attendant periodically drains the tank of its water by opening the valve. When the attendant drains the water from the tank, the attendant must drain the water through the drain conduit until he detects the presence of fuel being drained from the tank. At this point, the attendant knows that the water is sufficiently drained from the tank; however, the water drain conduit must become filled with fuel before the attendant is able to realize that the water has been properly drained. Thus, when the attendant drains the tank again, he must first draw off all the fuel that is trapped in the drain conduit before he detects that water is being drained from the tank.
The water and fuel drained from fuel storage tanks must be kept off the ground and prevented from draining into community sewer systems, etc. and must be disposed of. Many fuel storage areas include a special drain system to dispose of the fuel and water drawn off the fuel tanks wherein the fuel-water mixture is directed to a settling area so that the fuel and water will separate and the fuel can be recaptured and the water discarded. This prior art system of draining water from fuel storage tanks causes a lot of fuel to be wasted and requires the construction and operation of an expensive fuel-water separating system.